(a) Field of the Invention
The invention relates to an over-voltage protective device, and more particularly, to an over-voltage protective device for direct-current motor.
(b) Description of the Related Art
Direct-current (DC) motors are one of the most commonly applied motors in industrial use. Generally, the amount of current per unit time is raised to enhance rotational speed of DC motor for achieving expected operation efficiency. However, since DC motors are considered as one kind of inductive loads, the input voltages of DC motors are likely to be excessive as the amount of current per unit time is raised, and DC motor coils are prone to be damaged.